This program was developed from the need to define the added attenuation to frequencies above 10GHz caused by added attenuation through the atmosphere. Given that many Amateurs are venturing into frequencies where these effects become significant, this program provides the values required to increase the accuracy of the first principal calculations utilised in EMECalc.
This program [Atmosphere] calculates the absorption attenuation at Microwave frequencies for both terrestrial and slant paths for Amateur frequencies from 10-241 GHz. It has a Help documentation with the program.
It provides total path attenuation for both Home and Dx Stations in the form of :- Attenuation Free Space Path Loss + Attenuation caused by Oxygen + Attenuation due to Water Vapour + Attenuation due to Rain, fog and cloud. (of various intensities)
The calculations applied in this program are based upon the latest International Telecommunication Union (ITU) recommended methods as listed in the Reference section of the Help file Document.
The program [Atmosphere] is available from my web site (recently upgraded) www.vk3um.com
An upgraded version of EMECalc (Ver 7.14) may also be down loaded to apply the calculations provided by the ‘Atmosphere’ program.
Feed back would be appreciated, please.
73 Doug VK3UM
Background
Electromagnetic waves are absorbed in the atmosphere according to wavelength. Two compounds are responsible for the majority of signal absorption, Oxygen (O²) and water vapour (H²O).
The first peak occurs at 22 GHz due to water vapour, and the second at 63 GHz due to oxygen. The actual amount of water vapour and Oxygen in the atmosphere normally declines with an increase in altitude because of the decrease in pressure.
Total attenuation through the atmosphere at any frequency, through unobstructed atmosphere, is the sum of free space path loss, attenuation caused by oxygen absorption, and attenuation caused by water vapour absorption. Rain attenuation, when present adds an additional element.
http://www.vk3um.com/atmosphere%20calculator.html
